A poor start to the season has left the German champions tenth in the table and needing a win at Hamburg on Friday night to help make up the considerable ground behind Dortmund.
They are already 13 points behind the leaders and van Gaal says the need for points is growing ever urgent.
"Under these circumstances, we have to win," said van Gaal. "It is currently more important to win points than to play well."
The Dutchman has been buoyed by Germany striker Mario Gomez, who finally ended his 13 game goal-drought for Bayern with a hat-trick against Hannover last weekend.
The forward has now scored five goals in his last three games, having netted for Germany in a Euro 2012 qualifier and for Bayern against Cluj in the Champions League on Tuesday, and van Gaal is hoping for more goals from him.
While Hamburg are without injured Germany defender Dennis Aogo, Bayern are missing stars Franck Ribery (knee), Arjen Robben (thigh), captain Mark van Bommel (Knee) and Miroslav Klose (leg injury).
Dortmund face Hoffenheim on Sunday eager to protect their slender lead at the top of the table with second-placed Mainz also on 21 points, but with an inferior goal difference.
Borussia have just two days break between Thursday night's Europa League match against Paris St Germain and Sunday's Bundesliga match.
Fresh from their Champions League win over Tel Aviv on Wednesday, third-from-bottom Schalke are at Eintracht Frankfurt looking to avoid their sixth defeat in nine games so far this season.
Likewise, bottom side Stuttgart need to take some points from Sunday's home game against high-fliers St Pauli with new coach Jens Keller looking for his first win having taken over from Christian Gross before last weekend's draw with Schalke.
Werder Bremen will be without Germany goalkeeper Tim Wiese for their trip to Mönchengladbach on Saturday.
The shot-stopper faces a 10-day break after damaging medial ligaments in his right knee during the Champions League draw at FC Twente Enschede.
The 28-year-old limped out of his side's 1-1 draw in Holland on Wednesday night after just 36 minutes, but an MRI scan in Bremen has revealed he has only damaged medial ligaments.
In his absence, 21-year-old Sebastian Mielitz will take over between the posts.